The fire, burning in “thick debris,” was reported just after 7 a.m. in the 87000 block of Avenue 66. More than a dozen firefighters sent to the scene found one acre of green waste mulch piles ablaze, said April Newman of the Riverside County Fire Department.

Representatives from Riverside County Environmental Health and the Southern California Air Quality Management District also responded to deal with any potential public health risks that could arise from the fire, which had not been contained as of 10:15 a.m., Newman said.